A survey on Tannoy Dual Concentric Loudspeakers

The Point Source Approach

In the fast moving world of audio and hi-fi where new names seem to crop up every other month, it is refreshing to note that English loudspeaker manufacturer Tannoy is 75 years old. Throughout this long and illustrious history Tannoy have designed and manufactured a vast range of loudspeakers for professional audio monitoring, public address, live sound reinforcement and of course domestic audio.
Many design approaches have been featured but, for many, Tannoy is synonymous with dual concentric loudspeaker drivers.

The Tannoy range, even today, features many designs, but it is the dual concentrics which attract the most interest. Curiously, Tannoy have been promoting the virtues of a true point source design, as offered by the dual concentric drivers, for well over 40 years and yet it is only comparatively recently that other manufacturers (e.g. KEF with it's Uni-Q range) have successfully followed suit.
Note, we are speaking here of true point source designs, not simple concentric arrays.

The speaker pictured above is a Saturn S8LR from the current range. The author has a pair of DC1000s, a previous design featuring a similar sized (200mm) dual concentric driver which will be used for the purposes of this article.

I have been listening to Tannoys, either professionally or privately, for over 30 years and, while I have heard a great many other classic designs in that time, there is still something about the Tannoy sound that is at once unique and comfortable. That is not to suggest that Tannoy have stood still in that time. Far from it.
Steady evolution has seen the dual concentric reach new levels of performance and value as well as a broader range of potential applications. But those early
principles were so "right" that they are still highly relevant today.

There are several inherent virtues of the dual concentric design. The most obvious being the true point source emanation of sound waves which ensures a phase coherency not attainable by other means.
In conventional multi driver systems, the sound is emanating from different physical planes and positions, making off axis response rather variable. This is complicated by the cossover distributing different parts of the same sound to different physical drivers, which cannot help but to destroy the cohesiveness of the wavefront received at the listening position.
Imagine for example the sound of a viola playing a single musical line, reproduced via a typical two driver loudspeaker system. Part of the sound, including many of the fundamental frequencies, will be handled by the bass/mid driver and part of the sound will be handled by the
tweeter.
The problem is, even the lower frequency fundamentals will have harmonics way above the range of the bass/mid driver, which are passed to the tweeter. You therefore have spectral elements of the same note being reproduced by two very different drivers and reaching your ears at different points in time due to the different position of the drivers. This destroys absolute phase coherency and produces different effects at different axial positions.

With a true point source design there are little or no time and phase differences between harmonics either side of the crossover region.
Furthermore, there tends to be a more accurate balance between the fundamentals and harmonics, not only on axis, but even off axis, where many do a great deal of their listening. With the Tannoy dual concentric drivers there is a tight physical integration of the high and low
frequency drivers, leading to a coherent and linear phase response. This in turn means that a simpler crossover can be used, providing even greater sonic benefits.
It has long been understood that complex crossovers which attempt to provide phase alignment and other elements of control, invariably have negative effects upon sound transparency.

Sound

So much for the theory, but what do the Tannoy dual concentrics actually sound like? One of the reasons I have always loved Tannoys is for their vocal reproduction. If you have sensitive (to phase and other distortions) ears you will know that the human voice can present quite a
challenge to a hi-fi set up.
If it is a voice you are familiar with, you will understand that relatively few systems can accurately reproduce it (including the ones that require the re-mortgaging of your house). This is partly due to the complex harmonic structure of the human voice,
especially when singing a wide ranging piece of music.
In addition, a good voice has certain dynamic qualities which can easily be mangled
by hi-fi. The Tannoy dual concentric sound (even on the humble DC1000s) is phase coherent and reproduces voices well. Billie Holiday sounds like Billie Holiday. Dinah Washington sounds like Dinah Washington. A particularly dynamic and expressive voice such as Mahalia
Jackson is reproduced with a presence and clarity which many considerably more expensive systems cannot approach.
And it is not just vocals that benefit from this coherency. Instruments with complex harmonics such as brass and the higher register stringed instruments are
also reproduced with a natural presence. Furthermore, this quality is maintained and perceived over a wide axial response.
You can happily move around the room and still enjoy a great sound from these speakers.

Dynamics are also handled extremely well. This is an important area. Components that don't handle dynamics well are in effect introducing a particularly audible type of distortion. I hate the word "fast" when used in the context of audio reviews (components shouldn't be fast, slow or
anything else - they should be accurate) but those who bandy this word around will like the Tannoy sound. I suppose this is partly a virtue of the simple crossover used, but listen to a good recording of Buddy Rich on the Tannoys and then on anything else and you will get the picture.
They reproduce dynamics well. In fact, there is an interesting paradox here. Listen to Tannoy dual concentrics over a period of time and then listen to some of your favourite material on conventional multi driver designs and something sounds wrong, no matter how superficially
impressive the multi-driver set-up sounds. Tannoy also make (damn good) multi driver designs of course.
But for me, there will always be something special about the dual concentrics. If you are not familiar with the sound, I would encourage you to borrow a pair for a weekend or longer - showroom comparisons are meaningless, and discover a naturalness, vibrancy and coherency that you just might have been missing all these years. And now for a real treat, the Tannoy Westminster Royal, with it's 15 inch driver and 530 litre cabinet - ah, if only I had the space
for these....